[#316] locode: Define UN/LOCODE table data types

Define the data types needed to work with LOCODE's in NeoFS (country code,
location code, coordinates). Implement string parsers for new types.

Signed-off-by: Leonard Lyubich <leonard@nspcc.ru>

pkg/util/locode/column/location.go

@@ -0,0 +1,33 @@
+package locodecolumn
+
+import (
+	"github.com/nspcc-dev/neofs-node/pkg/util/locode"
+)
+
+const locationCodeLen = 3
+
+// LocationCode represents 3-character code for the location.
+type LocationCode [locationCodeLen]uint8
+
+// Symbols returns characters of the location code.
+func (lc *LocationCode) Symbols() [locationCodeLen]uint8 {
+	return *lc
+}
+
+// LocationCodeFromString parses string and returns location code.
+func LocationCodeFromString(s string) (*LocationCode, error) {
+	if len(s) != locationCodeLen {
+		return nil, locode.ErrInvalidString
+	}
+
+	for i := range s {
+		if !isUpperAlpha(s[i]) && !isDigit(s[i]) {
+			return nil, locode.ErrInvalidString
+		}
+	}
+
+	lc := LocationCode{}
+	copy(lc[:], s)
+
+	return &lc, nil
+}